The invention relates generally to the field of data communications and, more particularly, to methods of managing failover in a synchronous optical communications network.
In a synchronous optical communications network, interfaces between adjacent communications nodes can undergo degradation from a variety of sources. These sources include failures of physical link layer devices, inadvertent severing of the optical communications link, and a variety of other causes. When these failures occur, processing entities within the synchronous optical communications network must quickly failover to a secondary interface in order to minimize the information lost during the period prior to the transition to the secondary interface.
A typical technique for bringing about a failover in response to a degradation in the quality of the channel between adjacent communications nodes is to provide complete redundancy in all critical interface components. However, this requires additional complexity especially when each communications node is executing an application in which communications protocols are stacked one on top of another. Under these circumstances, applications which are executing within each communications node must be synchronized in order to bring about a graceful failover from one processing entity to another. Additionally, all state information used by each particular processing layer within the communications nodes must be conveyed to the secondary processing entity in order to enable processing operations to be harmonized within the network environment.
Complete redundancy in critical interface components also requires that any failover management applications be tailored to the particular processing environment of each type of communications node used within the synchronous optical communications network. Thus, network equipment providers are required to custom design equipment which operates at both ends of each optical communications link in order to ensure a harmonious failover of communications from one interface to another. This increases the cost and complexity in constructing reliable synchronous optical communications networks and, in turn, raises the cost of high quality data communications services provided to consumers.
Therefore, it is highly desirable to employ a method for link management in a synchronous optical communications network using standard protocols. This would allow network equipment providers to make use of standard equipment which operates using standardized rules for failover to secondary links. The method would additionally allow a reduction in the cost of implementing reliable synchronous optical communications networks, and thus benefits consumers who rely on these services.